1. Field of the Invention
The present invention relates to a gas rate sensor which is capable of detecting an angular velocity which has an effect on the gas rate sensor.
2. Description of the Prior Art
In general, a gas rate sensor provides an output signal in response to any difference between the output signals supplied from a pair of thermal sensing elements, which difference appears when the gas flow ejected from a gas nozzle deviates to flow more on one of the thermal sensing elements than on the other due to the influence on the gas flow by an applied motion whose angular velocity is to be determined in terms of its speed and direction.
The angular velocity is determined by detecting a small inbalance in the heat dissipation from the pair of thermal sensing elements due to the deviation of the gas flow, and therefore a surrounding temperature change has a great effect on the sensitivity of the gas rate sensor, particularly an adverse effect of lowering the sensitivity of gas rate sensor. This necessitates the use of temperature compensating means in the gas rate sensor.
In an attempt to reduce the adverse effect caused by the surrounding temperature the gas rate sensor is subjected to forced heating by using appropriate heaters, and the temperature within the gas rate sensor is detected by appropriate temperature sensors, and the temperature within the gas rate sensor is controlled so as to remain constant.
Disadvantageously, the sensitivity of the gas rate sensor and the offset value remain too unstable to provide correct output signals until the temperature within the gas rate sensor has reached a stable condition after connecting the electric heater to an associated power supply. As a matter of fact, no satisfactory gas temperature control has been attained.
With the above in mind one object of the present invention is to provide a gas rate sensor which is capable of correcting the gas rate sensor output signal in a most appropriate way to meet the instantaneous temperature change within the gas rate sensor, allowing the temperature within the gas rate sensor to vary.
To attain this object a gas rate sensor which can provide an output signal in response to any difference between the output signals from a pair of thermal sensing elements due to the effect which an angular velocity exerts on the gas flow ejected from an associated nozzle over the pair of thermal sensing elements, is improved according to the present invention in that said gas rate sensor is equipped with: means to effect temperature compensation of the gas rate sensor output signal by subtracting an offset value from the gas rate sensor output signal; means to determine the resistances of the pair of thermal sensing elements; means to detect the situation in which the resistances of the pair of thermal sensing elements increase or decrease simultaneously; means to make a decision as to whether or not the gas rate sensor output signal remains within a predetermined tolerance when such situation is detected; and means to permit the gas rate sensor output signal to be used as a new offset value when the gas rate sensor output signal remains within a predetermined tolerance.